Conventional mechanical gear generating machines for producing bevel and hypoid gears by generating or non-generating processes comprise a work support mechanism and a cradle mechanism. During a generating process, the cradle carries a circular tool along a circular path about an axis known as the cradle axis. The cradle represents the body of a theoretical generating gear and the cradle axis corresponds to the axis of the theoretical generating gear. The tool represents one or more teeth on the generating gear. The work support orients a workpiece relative to the cradle and rotates it at a specified ratio to the cradle rotation. Traditionally, conventional mechanical cradle-style bevel gear generating machines are usually equipped with a series of linear and angular scales (i.e. settings), which assist the operator in accurately locating the various machine components in their proper positions, which may include an adjustable mechanism that enables tilting of the tool spindle axis relative to the cradle axis.
More recently, gear producing machines have been developed which reduce the number of machine settings necessary to orient a tool relative to a workpiece. These machines replace some or all of the settings and movements of the conventional mechanical cradle-style machine with a system of linear, rotational, and/or pivoting (angular) axes. Typically, such machines are computer controlled multi-axis machines comprising at least six controlled axes for rotating a tool and a workpiece as well as positioning the tool and workpiece relative to one another for machining. Usually, three linear axes (usually mutually perpendicular) and three rotational and/or angular (i.e. pivot) axes are present on the multi-axis machines. Examples of such machines may be found in U.S. Pat. Nos. 4,981,402; 6,712,566; 5,961,260; 7,927,048 and U.S. Patent Application Publication No. 2006/0002775. Similar machine construction is also known for the so-called “machining centers” as shown, for example, in U.S. Pat. No. 6,752,573.
In some machines of the prior art, one or more linear axes have required travels beyond what is necessary for only the machining process. This “extra” axis travel is needed to obtain the necessary clearance for loading and/or unloading operations (manual or automated) and may necessitate the use of longer rails (guide ways) or the inclusion of machine components having large overhangs. The need for longer rails adds to the cost of machine manufacture and may increase the overall size (i.e. the “footprint”) of the machine. Component overhangs may threaten machine static or dynamic stiffness.
In other prior art machines, the manner of angular (pivoting) movement of one component may be cumbersome as it involves a pivoting mechanism located in the machining chamber where it may be exposed to machining by-products such as process fluids, metal chips and/or grinding swarf. In other machines, the angular movement of a component may require long axis rails and/or linear axis travel of large distances for other machine components in order to maintain proper workpiece/tool positioning. As stated above, the need for longer rails and their actuators (i.e. ball screws, feedback devices, etc.) adds to the cost of machine manufacture and may increase the overall size (“footprint”) of the machine. Additionally, long travel distances may result in additional cycle time to process a workpiece.